A constitutional crisis in Sri Lanka deepened on Saturday as President Maithripala Sirisena temporarily suspended parliament a day after sacking the prime minister and replacing him with a former leader seen as being close to China.

Sri Lankan President Maithripala Sirisena on Wednesday sacked the justice minister over his criticism of a $1.1 billion deal, signed last month, to lease a port to a Chinese company, the cabinet spokesman said.

Hundreds of hardline nationalists gathered outside the United Nations' office in the Sri Lankan capital Colombo on Saturday to protest against a visit by the UN human rights chief who will assess Sri Lanka's progress in prosecuting alleged war crimes.